First, related art of the present invention will be described. FIG. 9 is a cross sectional view of a facsimile apparatus using an ink-jet printing method. A print sheet 901 is placed on a print-sheet holder 903, and fed into the apparatus by a paper feed roller 904 and a separation mechanism (not shown) by one sheet. The fed print sheet 901 is conveyed by a conveyance roller 905 to a printing unit 906. The print sheet is discharged to the outside of the apparatus (in an arrow B direction) by a paper discharge roller 907 while image printing is performed on the print sheet by an ink-jet image printing mechanism.
On the other hand, a document 902 is placed on a document holder 908. At this time, the document 902 is set so as to abut on a wedge shaped portion formed with a document separation roller 909 and a separation piece 913. When the document separation roller 909 rotates in accordance with an image reading command, only one of plural documents 902 held with the wedge shaped portion which is in contact with the document separation roller 909 is separated by friction from the other documents 902 and conveyed. The separated and conveyed document 902 is further conveyed by a conveyance roller 910, then discharged to the outside of the apparatus (in an arrow A direction) by a paper discharge roller 912 while image information is read by a contact image sensor 911 or the like.
As the image quality of the document 902 is degraded with ambient light entered from a discharge port into the sensor 911, a light shielding sheet 900 is placed in slight contact with the document 902 for blocking the ambient light (stray light). Note that the contact between the light shielding sheet 900 and the document 902 is made such that the document 902 is not jammed in the apparatus.
Recently, there are increasing needs for downsizing and cost reduction of facsimile apparatuses. In studies to meet the requirements, it has been noted that in the above-described facsimile apparatus, a document conveyance mechanism and a print-sheet conveyance mechanism are separately provided.
That is, it has been considered that if the conveyance mechanism for conveyance of print sheet is also used as the conveyance mechanism for conveyance of document, the facsimile apparatus can be downsized. Since the conveyance roller, the paper discharge roller and the document driving motor and the like, provided for document conveyance can be omitted, this structure has seemed advantageous in downsizing and cost reduction.
However, this structure has problems. It is known that if an ink-jet method is used as the printing method, generally the discharge characteristic is more stable when ink is discharged right below in comparison with discharging in other directions. In this case, a print sheet is conveyed in a horizontal direction in a printing portion, since the print sheet is arranged in a direction orthogonal to the ink discharge direction. The image quality is improved if a document is read in a position as close to the conveyance roller as possible. Also, the image quality is improved if a print sheet is subjected to printing in a position as close to the conveyance roller as possible. In other words, to improve the image quality, it is preferable that a reading unit is positioned around the printing portion, and the reading unit is arranged in the horizontal direction.
In a case where the reading unit, which is an immobile but fixed unit, is positioned around the printing portion, a first problem is that a reference white board of the reading unit is soiled with ink upon printing.
For example, in facsimile apparatuses, generally a reference white board is read by prescanning for light amount control in the contact image sensor and acquisition of shading data. If the reference white board is soiled with ink in the prescanning, proper data cannot be obtained, and as a result, a read image is degraded.
Further, in some apparatuses, a movable reading unit is employed as disclosed in Japanese Published Unexamined Patent Application No. Hei 08-181820. However, as the reading unit is provided immediately below a printhead and driven upward/downward, if ink is erroneously discharged upon failure of conveyance of print sheet, the reference white board may be soiled with the discharged ink leaked through a platen board.
Further, a reading position of the above-described reading unit is in close vicinity to the paper discharge port of the document. As the ambient light (stray light) from the paper discharge port has a damaging effect on prescanning, a second problem is that a read image is degraded.
Further, as a third problem, if a paper jam with a document or print sheet occurs in the reading position, the document or print sheet disturbs a prescanning operation in the reading position.